1. Field of the Invention
The present invention relates to an anti-theft system adopted for vehicles such as automobiles, motorcycles, boats and the like.
2. Description of Related Art
Hitherto, as a vehicular anti-theft system, there is one, as disclosed in Japanese Patent Laid-Open No. 64-56248 (U.S. Pat. No. 4,965,460) for example, which keeps an engine which has once started running even if a supply of power voltage to an engine electronic control unit (hereinafter referred to as engine ECU) is unintentionally cut off, as long as a mechanical key is at a position of turning on an ignition switch, by maintaining the engine ECU on the ON state continuously by a security electronic control unit (hereinafter referred to as security ECU) by its holding circuit.
However, because the anti-theft system disclosed in Japanese Patent Laid-Open No. 64-56248 has the following problem as it is arranged so that after when the ignition switch is turned on, the security ECU sends an injection enabling signal for enabling to inject fuel to the engine to the engine ECU only once and the engine ECU shifts to a control of the injection of fuel after checking the transmission of the injection enabling signal from the security ECU by an initialization process along reset of its CPU.
That is, only a measure for preventing the stoppage of the engine during its operation is taken and no measure for a case when the CPU of the engine ECU is reset after the transmission of the injection enabling signal from the security ECU is taken in this system.
Accordingly, when the CPU of the engine ECU is reset when a power voltage of a car battery drops or is instantaneously cut off for example in activating a starter to start the engine, the injection enabling signal is not transmitted again as described above from the security ECU after when the power voltage has returned. Due to that, the injection of fuel is disabled. The same applies to a case when the CPU of the engine ECU is reset due to an abnormality thereof caused by an overrun of its function for example.
Further, as disclosed in Japanese Patent Laid-Open No. 3-32962, there is a vehicular anti-theft system which is arranged so that a function of an engine ignition system is stopped when a theft is detected and so that the function of ignition system is not stopped to hence keep running the engine once started when a circuit for detecting an operative state of the engine has detected the operative state of the engine.
The vehicular anti-theft system disclosed in Japanese Patent Laid-Open No. 3-32962 has a problem that the engine ignition system is also cut off in addition to the problem similar to the case described above.